This invention relates to belt drive systems and more particularly to such drive systems with a clutch for engaging and disengaging the drive engagement between the sheaves of the system. While such drive systems have a variety of applications, one application where the invention provides particular utility is in a mobile agricultural implement where an engagement and disengagement of the clutch is remotely controlled from the operator's station of the mobile implement.
One example of such an application is in self-propelled agricultural implements to transmit power from the engine of the self-propelled implement to the implement tools. For example, in a self-propelled windrower, such tools are a cutter for severing the crop from the field, conditioning rolls for conditioning the crop, and a reel for moving the crop from the cutter into the conditioning rows.
In the prior art such belt drives are commonly provided with a clutch so that the driving of the implement tools may be stopped independently of the engine of the self-propelled implement. There are two basic prior art methods for providing a clutch for belt drives, in general and also in common use, for such belt drives in self-propelled implements. One is the use of a movable idler pulley for slackening and tensioning the belt of the drive system. The second is the use of a movable drive sheave as one sheave of the belt drive so that the belt may be slackened and tensioned by movement of the sheave. When the drive system has a relatively short center-to-center distance between the drive sheaves of the system, there is often not enough room for a movable idler pulley to take up a sufficient amount of belt slack to permit adequate engagement and disengagement of the driving engagement between the sheaves. This problem is overcome typically by using the second of the two clutch types (i.e., movably mounting one of the drive and driven sheaves of the system and using it to provide a clutching action rather than using a movable idler pulley). This type of clutch will take up more belt slack than an idler with the same amount of motion.
The use of only a movable sheave (either drive or driven sheave of system) introduces two major problems. First, in a two-sheave drive, the total belt tension needed (tight plus slack side), whether at rest or in motion, must equal the total tension needed to transmit the peak power that is required. As a result, the bearings and drive belt must carry the same high tensile load regardless of the power required to be transmitted at any given time. When a movable, spring-loaded idler pulley is used as the clutch, the total tension required in the belt varies with the instantaneous power required. The idler maintains the tension constant in the slack side of the belt. The tension in the tight side of the belt varies from the minimum static tight side tension with the power required to be transmitted instantaneously such that the total tension in the belt (tight side plus slack side) equals the total tension required to transmit the instantaneous power required. Secondly, a two-sheave drive is limited to 360.degree. belt wrap. If an idler sheave is used, the belt wrap can be increased and therefore permit the transmission of higher power requirements with no increase in tension in the belt (relative to the two-sheave system).
Accordingly, it is an object of this invention to overcome the disadvantages of both clutch types by providing a belt drive system (including a clutch) which uses both a movable drive sheave clutching action and a movable, spring-loaded idler sheave clutching action.
Another object of this invention is to provide for a belt drive system having a very short center-to-center distance between the sheaves of the drive system and a clutch which permits sufficient belt length to be taken up and released to provide a clutching action.
Still another object of the invention is to provide a belt drive system wherein the total belt tension varies as a function of the instantaneous power.
Still another object of the invention is to provide a belt drive system having a short center-to-center distance between the drive and driven sheaves with improved drive component life.
Still another object of the invention is to provide a belt drive system having a short center-to-center distance between the drive and driven sheaves with more than a 360.degree. belt wrap on the drive and driven sheaves.